I got a tip from a waitress and I find it to be so useful that I wanted to share it with everyone. Unfortunately, I do not remember her name to give her proper credit.
You know how annoying it is when you have a cold drink and you lift the glass/bottle from the table, and the napkin/coaster is lifted along with the glass? Well, next time, simply sprinkle some salt on the napkin and never again will the napkin glue itself to your glass. :-)